Method for repairing pattern defect, photo mask using the method, and semiconductor device manufacturing method employing the photo mask

ABSTRACT

A new method for repairing pattern defect on a photo mask is provided. The method includes the steps of: (a) determining the irradiation area of the focused ion beam (FIB) directed towards a defect, by narrowing the irradiation area by a predetermined distance inwardly from the edge of the defect; (b) focusing the FIB onto its irradiation area to remove a part of the pattern film material of the defect from its top surface and thus leave a thin layer on a mask substrate; and (c) removing the thin layer by using a laser beam. The defect may be an isolated pattern or a pattern extended continuously from an edge of the normal pattern. Further, the photo mask repaired by the method, and a manufacturing method of semiconductor devices employing the repaired photo mask are proposed. The photo mask may include a phase shift mask.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for repairing a pattern defecton a photo mask, the photo mask repaired by the repairing method, and amanufacturing method of semiconductor devices employing the repairedphoto mask. The photo mask may include a phase shift mask.

2. Description of the Related Art

In the manufacturing method of the semiconductor devices such as largescale integrations (LSls), very large scale integrations (VLSIs), ultralarge scale integrations (ULSIs), and giga scale integrations (GSIs), aset of photo masks or reticles is required for photolithography steps.Each of the photo masks is composed of predetermined patterns made of alight-shielding layer or phase shift layer arranged on a transparentmask substrate, such as a quartz substrate. During the fabricationprocess of the photo masks, miscellaneous microscopic defects 6 a, 6 b,6 c may be created on the mask substrate as shown in FIGS. 1A, 1B and1C, for example. In each of FIGS. 1A to 1C, three lines 3 a, 3 b, and 3c made of the light-shielding layer are shown, sandwiching spaces 4 and4 between them. In FIG. 1A, a defect 6 a protruding from the left edgeof line 3 b is shown. In FIG. 1B, an isolated defect 6 b is shown, butvery close to the left edge of line 3 b. And in FIG. 1C, an isolateddefect 6 c is shown disposed midway between lines 3 a and 3 b. Thedefects 6 a, 6 b, 6 c can be commonly evaporated and eliminated whenexposed to a laser beam. As a result of the exposure to a laser beam,the left edge of line pattern 3 b may develop “a mouse-nip” or “arat-bite” as shown in FIG. 2A. Or, although not shown, the left edge ofline pattern 3 b may develop a peeling. Or, an edge-roughness may becreated on the left edge of line 3 b as shown in FIG. 2B, which fails tofinish in a desired normal line shape. As the feature size of such aphoto mask pattern becomes significantly finer and finer, its repairingprocess at a high accuracy will be very difficult with a laser beamscanning precisely along the edge of the line pattern. Also, since thefocusing of the laser beam is limited, the pattern defect repairing athigher accuracy, which may require a laser beam diameter finer than 0.5μm, will thus be a troublesome task.

Also, mask repairing for removing defects may be carried out by asputtering method using a focused ion beam (FIB). It is known that whenthe ion beam is directed to an irradiation area on the mask substratemade of quartz, its gallium (Ga) ions from an ion source are implantedinto the quartz substrate, which generates gallium stains and hencedecreases the transparency of the substrate. Moreover, the diffused FIBand the beam expansion of the FIB may result in excessive etching aroundthe perimeter of the microscopic defect that needs to be eliminated. Theexcessive etching generally produces V-shaped grooves around theperiphery of the microscopic defect, which are also known as“riverbeds.”

For solving the above problems, etching a chromium (Cr) film by “a gasassisted FIB etching process” is proposed as the pattern defectrepairing method for removing the microscopic defect generated on achromium mask. (K. Aita et al., SPIE, vol. 2512, p. 412 (1995), and J.David Casey, Jr. et al., SPIE, vol. 3096, pp. 322-332 (1997)). Here, thechromium mask has the light-shielding layer of a chromium (Cr) film or achromium compound film such as chromium oxide (CrO_(x)) film fordelineating the required pattern on the quartz substrate. By the gasassisted FIB etching process, the gallium stains or riverbeds arereported to have been eliminated. It is reported that a mask patternrepaired by the above-mentioned pattern defect repairing method couldproduce an acceptable image level projected with an i-line at awavelength of 365 nm. In the gas assisted FIB etching process, anetching gas is employed with a high selectivity of etching rates betweenthe mask substrate and the chromium film or the chromium oxide film.

However, it was found that, in finer masks used for exposure by Deep UV(DUV) rays or further shorter wavelength rays, the chromium filmrepaired by the gas assisted FIB etching process still has noticeabledamages to the mask substrate, attributable to the gallium stains or theriverbed.

FIG. 3 is a plan view of a repaired photo mask corresponding to FIG. 1A,which has been repaired by the gas assisted FIB etching process. Thechromium mask 1 has an etching burn 5 a generated at the aperture 4,very closely disposed to the left edge of line 3 b, from removing themicroscopic defect 6 a with the gas assisted FIB etching process. FIG. 4is a diagram showing the image intensity profile taken along the lineIII—III of FIG. 3 on a wafer on which an image of the repaired maskpattern is projected. The ordinate in FIG. 4 represents the intensity ofthe projected image and the abscissa represents locations on the wafer(along a predetermined axis, such as the X axis). In FIG. 4, “S”represents the position of the repaired space between lines 3 a and 3 b,and “L” represents the position of line 3 b. It is assumed that theexposure conditions in a stepper loading the chromium mask (reticle) areas follows:

[007] the exposure wavelength λ = 248 nm; [008] the aperture number NA =0.6; and [009] the coherence factor γ = 0.75.

As apparent from FIG. 4, the intensity at the etching burn 5 a in theaperture of the repaired mask is decreased by more than 20% from that ofa non-defect region of the mask. In this way, the unrequired etchingburn 5 a was unfavorably transferred onto the wafer.

The gas assisted FIB etching process may rarely be effective forrepairing microscopic defect on a phase shift mask when it is made of asilicon based material such as molybdenum silicide (MoSi, or MoSi_(x))and used as the film material for producing the light-shielding patternor the phase shifter pattern. In a step of imaging with the FIB, thephase shifter film may easily be charged up thus interrupting theprojection of an image at a higher signal to noise (S/N) ratio andrendering the end point of the etching process hardly detectable with ahigher accuracy.

SUMMARY OF THE INVENTION

The present invention has been achieved with a view of the foregoingfeatures and its object is to provide a method for repairing a patterndefect, in which the damage against the transparent substrate of a maskis minimized.

Another object of the present invention is to provide a method forrepairing a pattern defect, in which the etching of the surface of thetransparent substrate of a mask is minimized.

It is still another object of the present invention to provide a methodfor repairing a pattern defect, suppressing a change in the imageintensity through the mask, thereby having a favorable level of thewafer process margin.

It is still another object of the present invention to provide a photomask having fine pattern and a high transmissivity, having uniform imageintensity profiles.

It is still another object of the present invention to provide a methodfor manufacturing semiconductor devices having miniaturized featuresizes, with a favorable level of the process margin in the lithographyprocess.

A first feature of the present invention involves a method for repairinga defect generated on a mask substrate. The defect may be isolated fromnormal patterns, or continuous excess patterns protruding from the edgeof the normal pattern. More particularly, the method for repairing thepattern defect according to the first feature of the present inventioncomprises the steps of: (a) determining the irradiation area of an ionbeam directed towards a defect by narrowing the irradiation area by apredetermined distance inwardly from the edge of defect; (b) focusingthe ion beam onto its irradiation area to remove a part of the defectfrom its surface so as to leave a thin layer of the defect on the masksubstrate; and (c) removing the thin layer by using a laser beam.

According to the first feature of the present invention, a portion ofthe defect is etched by a FIB process capable of etching locally at ahigher accuracy and fineness. Namely, a gas assisted FIB etching processor a FIB sputtering process may be used. While the predetermineddistance from the edge of the defect inwardly narrows the irradiationarea of the ion beam, the thin layer of the pattern film material isleft so that the mask substrate beneath and around the defect is notexposed to the FIB, and then the thin layer is eliminated by exposure tothe laser beam. Accordingly, the repairing method according to the firstfeature of the present invention enables one to perform the repairingprocess at a higher accuracy and processing facilitation withoutproducing peelings, rat-bites, or edge-roughness. In fact, the patternfilm material of the defect next to the edge of the normal pattern iscompletely eliminated, hence allowing the edge of the normal pattern tobe contoured with a higher precision and a better finish. Also, thepattern defect repairing method according to the first feature of thepresent invention develops the thin layer, hence minimizing theimplantation of FIB ions into the transparent mask substrate and thedigging of the surface of the mask substrate. The thickness of the thinlayer is smaller than that of the light-shielding pattern, allowing thelaser beam to give minimum damage to the mask substrate. Damage to themask substrate may result in deterioration of the transparency of themask substrate. As damage to the mask substrate is kept to a minimum, achange in the image intensity caused during the pattern defect repairingcan be suppressed, hence it is possible to provide a favorable level ofthe wafer process margin.

The second feature of the present invention lies in a photo mask,repaired by the method explained by the first feature. Namely, the photomask of the second feature has a mask substrate having a substantiallyflat surface and pattern delineated on the mask substrate, the patternhas an edge, the edge has a localized specific side wall having aninclination angle differing from that of the remaining sidewall. Thelocalized specific sidewall corresponds to the repaired portion, and caneasily be recognized, since the specific sidewall is brighter than otheredges in reflective images. The decrease in the image intensity throughthe mask substrate neighboring the specific sidewall is not higher than5% compared with that of other portion, since damage to the masksubstrate is kept to a minimum.

The third feature of the present invention lies in a method formanufacturing semiconductor device comprising the steps of: (a)generating pattern on a mask substrate so as to fabricate a photo mask;(b) inspecting a pattern defect on the mask substrate; (c) repairing apattern defect by the method already stated in the first feature; and(d) fabricating a semiconductor device employing the repaired photomask.

Other and further objects and features of the present invention willbecome obvious upon an understanding of the illustrative embodimentsabout to be described in connection with the accompanying drawings, orwill be indicated in the appended claims, and various advantages notreferred to herein will occur to one skilled in the art upon employingthe invention in practice.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a plan view of a mask pattern showing a example of patterndefect formed on the mask substrate;

FIG. 1B is a plan view of a mask pattern showing another example ofpattern defect formed on the mask substrate;

FIG. 10C is a plan view of a mask pattern showing still another exampleof pattern defect formed on the mask substrate;

FIG. 2A is a plan view of a mask pattern, explaining a conventionalmethod for repairing a mask defect, in which “a rat-bite” is formed atthe pattern edge;

FIG. 2B is a plan view of a mask pattern, explaining a conventionalmethod for repairing a mask defect, in which “edge-roughness” is formedat the pattern edge;

FIG. 3 is a plan view of a mask pattern explaining a conventional methodfor repairing a mask defect;

FIG. 4 is a diagram showing a profile of image intensity taken along theline III—III of FIG. 3;

FIG. 5 illustrates a plan view (a) and a cross sectional view (b) takenalong the line V—V of the plan view (a), showing a chromium mask havinga microscopic defect which is to be repaired according to the presentinvention;

FIG. 6A is a cross section view of the chromium mask explaining a maskdefect repairing method according to a first embodiment of the presentinvention;

FIG. 6B illustrates a plan view (a) and a cross sectional view (b) takenalong the line VI—VI of the plan view (a), explaining the mask defectrepairing method according to the first embodiment of the presentinvention;

FIG. 6C is a plan view of the chromium mask explaining the mask defectrepairing method according to the first embodiment of the presentinvention;

FIG. 6D illustrates a plan view (a) and a cross sectional view (b) takenalong the line VI—VI of the plan view (a), explaining the mask defectrepairing method according to the first embodiment of the presentinvention;

FIG. 7A shows the relation between the detected secondary chromium ionsand dose amount;

FIG. 7B shows the variation of the transmissivity of the repairedportion by the change of the end point detection level in the gas assistFIB etching of the chromium film.

FIG. 8A is a diagram showing a profile of the image intensity on a waferexposed to an image of the mask pattern repaired by the method of thefirst embodiment of the present invention;

FIG. 8B is a diagram showing process windows at 10% of the exposuremargin, calculated from the profile shown in FIG. 8A;

FIG. 9 illustrates a plan view (a) and a cross sectional view (b) takenalong the line IX—IX of the plan view (a), showing a phase shift maskhaving a microscopic defect which is to be repaired according to thepresent invention;

FIG. 10A is a cross sectional view of the phase shift mask explaining amask defect repairing method according to a second embodiment of thepresent invention;

FIG. 10B illustrates a plan view (a) and a cross sectional view (b)taken along the line X—X of the plan view (a), explaining the maskdefect repairing method according to the second embodiment of thepresent invention;

FIG. 10C is a plan view of the phase shift mask explaining the maskdefect repairing method according to the second embodiment of thepresent invention;

FIG. 10D illustrates a plan view (a) and a cross sectional view (b)taken along the line X—X of the plan view (a), explaining the maskdefect repairing method according to the second embodiment of thepresent invention;

FIG. 11A illustrates a plan view (a) and a cross sectional view (b)taken along the line XI—XI of the plan view (a), explaining the maskdefect repairing method according to the modification of secondembodiment of the present invention;

FIG. 11B is a cross sectional view of the phase shift mask explainingthe mask defect repairing method according to the modification of thesecond embodiment of the present invention;

FIG. 11C illustrates a plan view (a) and a cross sectional view (b)taken along the line XI—XI of the plan view (a), explaining the maskdefect repairing method according to the modification of secondembodiment of the present invention;

FIG. 12A is a cross sectional view of the phase shift mask explaining amodification of the mask defect repairing method according to themodification of the second embodiment of the present invention;

FIG. 12B is a cross sectional view of the phase shift mask explainingthe modified mask defect repairing method according to the modificationof the second embodiment of the present invention;

FIG. 13A illustrates a plan view (a) and a cross sectional view (b)taken along the line XIII—XIII of the plan view (a), explaining the maskdefect repairing method according to the third embodiment of the presentinvention;

FIG. 13B is a cross sectional view of the phase shift mask explainingthe mask defect repairing method according to the third embodiment ofthe present invention;

FIG. 13C illustrates a plan view (a) and a cross sectional view (b)taken along the line XIII—XIII of the plan view (a), explaining the maskdefect repairing method according to the third embodiment of the presentinvention;

FIG. 13D is a plan view of the phase shift mask explaining the maskdefect repairing method according to the third embodiment of the presentinvention;

FIG. 13E illustrates a plan view (b) and a cross sectional view (a)taken along the line XIII—XIII of the plan view (b), explaining the maskdefect repairing method according to the third embodiment of the presentinvention;

FIG. 13F is a cross sectional view of the phase shift mask explainingthe mask defect repairing method according to the third embodiment ofthe present invention; and

FIG. 13G is a cross sectional view of the phase shift mask explainingthe mask defect repairing method according to the third embodiment ofthe present invention.

FIG. 14 illustrates a plan view (a) and a cross sectional view (b) takenalong the line XIV—XIV of the plan view (a), explaining the mask defectrepairing method according to the fourth embodiment of the presentinvention;

FIG. 15A illustrates a plan view (a) and a cross sectional view (b)taken along the line XV—XV of the plan view (a), showing a chromium maskhaving an isolated defect which is to be repaired according to thefourth embodiment of the present invention;

FIG. 15B illustrates a plan view (a) and a cross sectional view (b)taken along the line XV—XV of the plan view (a), explaining the maskdefect repairing method according to the fourth embodiment of thepresent invention;

FIG. 16 illustrates an image intensity profile taken along line XV—XV ofFIG. 15B;

FIG. 17 illustrates an image intensity profile taken along line XV—XV ofFIG. 15B, after the thin chromium film is etched away by acid solution;

FIG. 18 illustrates a simplified flowchart for manufacturingsemiconductor devices;

FIG. 19 illustrates details of the semiconductor device manufacturingprocess; and

FIG. 20 illustrates a relatively simple manufacturing processes of annMOS FET.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the present invention will be described withreference to the accompanying drawings. It is noted that the same orsimilar reference numerals are applied to the same or similar parts andelements throughout the drawings, and the description of the same orsimilar parts and elements will be omitted or simplified. Generally, andas is conventional in the representation of photo masks, it will beappreciated that the various drawings are not drawn to scale from onefigure to another nor inside a given figure, and in particular that thelayer thicknesses are arbitrarily drawn for facilitating the reading ofthe drawings. In the following descriptions, numerous specific detailsare set fourth such as specific signal values, etc., to provide athorough understanding of the present invention. However, it will beobvious to those skilled in the art that the present invention may bepracticed without such specific details.

FIRST EMBODIMENT

As shown in FIG. 5, a mask repaired by a first embodiment of the presentinvention has chromium light-shielding lines 3 a, 3 b and 3 c delineatedon a transparent quartz substrate 2. In details, each of the chromiumlight-shielding lines 3 a, 3 b and 3 c is composed of a layeredstructure consisting of a chromium layer and a chromium oxide layerprovided on the chromium layer. The layered structure is referred as“the chromium light-shielding layer”, or“the chromium light-shieldingline” hereinafter. The mask in the first embodiment of the presentinvention is 4× the size of circuit to be printed on a wafer. In thefirst embodiment of the present invention, the line width of thechromium light-shielding lines 3 a, 3 b and 3 c is assumed to be 0.9 μmand the width of the space portion 4 is assumed to be 1.1 μm. And themicroscopic defect 6 a is extending from the left edge of the line 3 b.It is commonly appreciated that more intricate rectangle patterns thansuch a simple line and space pattern may equally be employed.

The mask defect repairing method according to the first embodiment ofthe present invention will now be described. Here, an excessive portionof the pattern film material, or the microscopic defect 6 a generated onthe chromium mask 1, will be eliminated. The chromium mask 1 has thechromium light-shielding lines 3 a, 3 b and 3 c delineated on the quartzsubstrate 2 as shown in FIG. 5.

(a) First, as shown in FIG. 6A, the microscopic defect 6 a is sputteredby a FIB 7 with an assistant gas 8 for chromium film etching. Theassistant gas 8 is sprayed over the mask surface. In other words, a gasassisted FIB etching process carries out the etching. As described inthe section of BACKGROUND OF THE INVENTION, riverbeds may possibly becreated around the microscopic defect 6 a by the effect of a diffusedFIB or beam expansion of the FIB. For compensation, the exposure areaabout the microscopic defect 6 a to the ion beam, directed towards thetransparent quartz substrate 2, is inwardly narrowed by 0.3 nm to 200 nmfrom the edge of the microscopic defect 6 a. Preferably, it is narrowedby a half of the FIB diameter. As FIB ion source, gallium ions areemployed. The FIB has an accelerating voltage of 20 kV and a current of50±10 pA with a beam diameter 0.2 μm. As half of the beam diameter ofFIB is 0.1 μm, the exposure area to the ion beam is inwardly narrowed by100 nm from the edge of the microscopic defect 6 a. The end point of theetching is determined by counting the number of chromium ions in theetched region with a secondary ion detector. As the etching proceeds,reduced the thickness of a chromium light-shielding layer of themicroscopic defect 6 a approaching the point where the surface of thequartz substrate is exposed, and the number of chromium ions decreasesas shown in FIG. 7A. In FIG. 7A, the detected secondary chromium ionsare normalized to the secondary chromium ions at starting point ofetching. The dose amount by which the chromium light-shielding film iscompletely removed is shown by vertical line. When the quartz substratebeneath the chromium light-shielding layer appears, the number ofchromium ions drops below the noise level. FIG. 7B shows the variationof the transmissivity of the repaired portion by the change of the endpoint detection level in the gas assist FIB etching of the chromiumfilm. The abscissa represents the end point detection level, whichdefines the level at which the etching is to be finished. Namely the endpoint detection level is defined as a ratio (%) of the chromiumsecondary ion count number under etching to the initial chromium ioncount number. The ordinate represents the normalized transmissivity ofthe repaired portion, taking the transmissivity of quartz substrate tobe 1. In FIG. 7B, it is shown that the transmissivity becomes higher asthe end point detection level is higher. In short, transmissivitylowering by the gas assist FIB etching of the chromium is smaller, whena thin film remains, such that the chromium secondary ion can bedetected, as opposed to the case where the etching has proceeded to thepoint where the surface of the quartz substrate is nearly exposed. Inthe pattern defect repairing method of the first embodiment of thepresent invention, the etching is finished when the number of chromiumions is decreased to 70 to 80% in the end point detection level, beforethe quartz substrate beneath the microscopic defect 6 a is completelyexposed to the FIB 7.

(b) As a result, a thin chromium film 9 a remains where the microscopicdefect 6 a was present. The judgment over the end of the etching isdelayed more in an edge region of the microscopic defect 6 a adjacent tothe pattern of the light-shielding line 3 b than in a central region ofthe microscopic defect 6 a, because some of the chromium ions in thelight-shielding line 3 b close to the microscopic defect 6 a may bedetected at the same time. This allows the etching action to becontinued in the adjacent edge region of the microscopic defect 6 awhile it is terminated in the central region. Accordingly, the adjacentedge region of the microscopic defect 6 a can be etched until the uppersurface of the quartz substrate 2 appears, leaving no sign of thechromium film. On the other hand, the number of chromium ions is morequickly reduced in an edge region opposite to the adjacent edge regionof the microscopic defect 6 a than in the central region. Hence, theopposite edge region will remain thicker, giving an uneven profile ofthe thickness of the microscopic defect 6 a. That is, an uneven thinchromium film 9 a is left after the gas assisted FIB etching of themicroscopic defect 6 a, as shown in FIG. 6B. More typically, theperimeter of the thin chromium film 9 a of the microscopic defect 6 aranges from 15 nm to 30 nm. The thickness of the central region of themicroscopic defect 6 a after the gas assisted FIB etching is smallerthan 30 nm, for example, substantially 0.3 nm to 5 nm. As shown in FIG.6B, the light-shielding line 3 b has an oblique sidewall at the leftedge, differing from that of the remaining vertical sidewall of thelight-shielding lines 3 a and 3 c. The oblique sidewall corresponds tothe repaired portion, and is easily recognized, since the obliquesidewall is brighter than other vertical edges in reflective images.Although it may depend on the etching condition of after the gasassisted FIB etching, the oblique angle of the sidewall at the repairedportion may be less than 10 degrees from the normal direction (or theperpendicular direction) of the mask substrate. The light-shielding line3 b has the vertical sidewall at the right edge, obviously. By theexistence of the bright oblique sidewall at the repaired portion, theleft edge of the light-shielding line 3 b may show a small bite in aplan view, but the bite is so small that the left edge of thelight-shielding line 3 b can be regarded as a straight line in apractical sense of photolithography. Actually, the bright obliquesidewall at the repaired portion cannot easily be recognized intransmission images.

(c) Then, as shown in FIG. 6C, a laser irradiation area 10 is determinedfor removing the thin chromium film 9 a by exposure to laser. No thinchromium film 9 a remains in the adjacent edge region of the microscopicdefect 6 a as shown in FIG. 6B, allowing the quartz substrate 2 toappear. Therefore, the exposure to laser is not needed in the adjacentedge region of the microscopic defect 6 a. The laser irradiation area 10is so sized as not to overlap the pattern of the chromiumlight-shielding line 3 b but to cover the thin chromium film 9 a of themicroscopic defect 6 a as shown in FIG. 6C. As a laser beam is directedto the laser irradiation area 10 spaced by a given distance from thepattern of the chromium light-shielding line 3 b, it falls on and etchesthe thin chromium film 9 a of the microscopic defect part. Accordingly,the thin chromium film 9 a is eliminated as shown in FIG. 6D. In themethod of the first embodiment of the present invention, the laserirradiation area 10 is determined over the thin chromium film 9 a of themicroscopic defect 6 a, which is spaced from the pattern of the film 3b, as shown in FIG. 6C, thus not requiring a higher level of theaccuracy for focusing the beam of a laser mask defect repairingapparatus. Also, peeling, rat-bites, or edge-roughness on edge regionsof the pattern of the chromium light-shielding line 3 b caused bymisalignment of the laser beam or the like may be avoided. As statedabove, by the existence of the bright oblique sidewall at the repairedportion, the left edge of the light-shielding line 3 b may show themicroscopic bite in the plan view, but the bite is so small that theleft edge of the light-shielding line 3 b cannot be regarded as therat-bites in a practical sense of photolithography. The thickness of thethin chromium film 9 a is substantially 30 nm at maximum and muchsmaller than that of the chromium light-shielding lines 3 a, 3 b and 3c, which are typically 100 nm. Accordingly, damage to the mask caused byexposure to the repairing laser will be minimized as compared with aconventional method in which the microscopic defect is equal inthickness to the pattern light-shielding layer.

FIG. 8A illustrates a profile of the image intensity on a wafer takenalong the line VI-VI of FIG. 6D(a) when the laser of wavelength of 248nm is focused through a mask pattern repaired by the method of the firstembodiment of the present invention. The profile of the image intensitycan be measured using an aerial image measurement system for variousdefocus positions of 0.0, ±0.2, ±0.4, ±0.8, and ±1.0 μm. Characteristicexamples of the image measurement system applicable for the purposeinclude a Carl Zeiss Microlithography Simulation Microscope (“MSM-100”).The image measurement system has a CCD sensor disposed over a wafer formeasuring the intensity of light passing through a reticle under thesame exposure conditions as that of a stepper. The ordinate in FIG. 8Arepresents the image intensity and the abscissa represents the Xposition in micrometers (μm) on the wafer. The exposure conditions inthe stepper are as follows:

[070] the exposure wavelength λ = 248 nm; [071] the aperture number NA =0.6; and [072] the coherence factor γ = 0.75.

The position “S” in FIG. 8A corresponds to the space portion 14 (therepaired mask space shown in FIG. 6D) in the repaired mask, and itexhibits a decrease in the image intensity, not higher than 5% comparedwith that of the non-defect region, or the normal portion. The position“L” in FIG. 8A corresponds to the repaired mask line 3 b shown in FIG.6D.

FIG. 8B shows the relationship between exposure intensities anddefocusing distances obtained from the profile of the image intensityshown in FIG. 8A. The abscissa in FIG. 8B represents an inverse of thethreshold relative to the exposure intensity obtained from FIG. 8A. Morespecifically, the threshold defines a ratio between the line and space,and the threshold becomes smaller as the exposure intensity increases asshown in FIG. 8A. The higher the inverse of the threshold, the more theexposure intensity increases. In fact, FIG. 8B illustrates therelationship between the exposure intensity of light and the defocusingpoint (distance) when the pattern consisting of the space portion 14(the repaired mask space) and the light-shielding layer 3 b (therepaired mask line) is focused at 0.25 μm ±10% on the wafer. Also, FIG.8B shows process windows at 10% of the exposure margin defined by therelationship between the exposure intensity and the defocusing position.The focal depth (FD) is 1.34 μm when the exposure margin is 10% in theprocess window for the non-defect pattern while the FD=1.12 μm in acommon process window for the repaired mask pattern and the non-defectpattern (at 10% of the exposure margin). It is thus apparent that therepaired mask pattern becomes 80% or more of the non-defect pattern inthe FD.

The method for repairing a pattern defect according to the presentinvention is not limited to the line and space pattern, the maskmagnification (or reduction system), and the type and size of defectdescribed with the first embodiment, but may successfully be applicableto any repairing of defects on a mask when the pattern film material isselected from chromium materials. As set forth above, the method forrepairing a pattern defect according to the first embodiment of thepresent invention is applicable to any defect on a chromium mask to beeliminated at higher precision and geometrical accuracy, withoutdamaging the mask substrate. As a result, a change in the intensity of aresultant pattern image caused by the repaired region of the mask willbe minimized and a favorable level of the wafer-processing margin willbe gained.

SECOND EMBODIMENT

A second embodiment of the present invention will be described in theform of a mask defect repairing method of eliminating a microscopicdefect 6 a generated on a phase shifter 17 b made of an oxide nitride ofmolybdenum silicide (MoSiO_(x)N_(y)) as a pattern film materialdelineated on a quartz substrate 2. Instead of MoSiO_(x)N_(y), an oxideof molybdenum silicide (MoSiO_(x)), or composite film ofMoSiO_(x)N_(y)/MoSi and MoSiO_(x)/MoSi can also be employed for thephase shifter 17 b. The molybdenum silicide phase shifter 17 b isreferred to as “the phase shifter 17 b” hereinafter. And a molybdenumsilicide phase shifter pattern may be called as “a phase shifterpattern”.

A phase shift mask 16 shown in FIG. 9 comprises the line pattern ofphase shifter 17 b made of the oxide nitride of molybdenum silicide andanother line patterns 17 a and 17 c delineated on the transparent quartzsubstrate 2. The line patterns 17 a and 17 c can be made of the oxidenitride of molybdenum silicide. The mask pattern includes the spacepattern 4 sandwiched between lines 17 a and 17 b, and the space pattern4 sandwiched between lines 17 b and 17 c. It is assumed that themicroscopic defect 6 a extends from the left edge of the line pattern 17b as shown in FIG. 9.

(a) First, as shown in FIG. 10A, the microscopic defect 6 a is etched bysputtering. At FIB 7, gallium ions with an accelerating voltage of 20kV, a current of 50±10 pA, and a beam diameter of 0.2 μm φ are employed. Considering that there may possibly be created riverbeds around theperimeter of the microscopic defect 6 a, the exposure area for the FIBdirected towards the transparent quartz substrate 2 is narrowed by 0.3nm to 200 nm from the edge of the microscopic defect 6 a. That is, theexposure area is inwardly shrunk by 0.3 nm to 200 nm from the far sideedge of the microscopic defect 6 a, except for the edge next to the line17 b. Preferably, it is inwardly shrunk by a half of the beam diameterof the FIB. For example, the exposure area is inwardly narrowed by 100nm, corresponding to a half of the beam diameter from the edge of themicroscopic defect 6 a. Also, the etching is controlled to have a thinlayer of the molybdenum silicide film remained not higher than 30 nm ofthe thickness of the microscopic defect 6 a in order to prevent thequartz substrate 2 beneath the microscopic defect 6 a from being exposedcompletely. As a result, a gallium doped molybdenum silicide layer 18derived from the microscopic defect 6 a is left.

(b) Then, as shown in FIG. 10C, the irradiation area 10 of a laser beamis determined not to overlap the pattern edge of the phase shifter 17 b.The laser beam is directed to the laser irradiation area 10 to removethe gallium doped molybdenum silicide layer 18. The gallium dopedmolybdenum silicide layer 18 contains gallium ions implanted by the FIBand enables the absorption of more energy of the laser beam, thus thelayer is eliminated with higher efficiency. This permits the galliumdoped molybdenum silicide layer 18 to be eliminated without controllingthe irradiation area of the laser beam to run directly beside (andalong) the edge of the pattern. After this step, the repaired maskpattern is obtained as shown in FIG. 10D.

The method for repairing pattern defect according to the presentinvention is not limited to the mask pattern, the mask magnification,the type and size of defect, and the pattern film material describedwith the second embodiment, but may successfully be applicable to anyrepairing of a microscopic defect on a mask.

As set forth above, the second embodiment of the method for repairing apattern defect according to the present invention allows any microscopicdefect on a molybdenum silicide phase shift mask to be eliminated athigher precision and processing facilitation without damaging the masksubstrate. As a result, a change in the intensity of a resultant patternimage caused by a repaired region of the mask will be minimized and afavorable level of the wafer-processing margin will be gained.

While the etching of a microscopic defect by the FIB sputtering of thesecond embodiment produces a gallium doped molybdenum suicide layer, amodification of the second embodiment of the present invention isdescribed, wherein a microscopic defect of the oxide nitride film hascompletely been removed, and a region of the quartz substrate from whichthe microscopic defect is eliminated develops a thin surface layer ofgallium-doped quartz.

A phase shift mask 16 repaired by the modification of the secondembodiment of the present invention is composed of a group of molybdenumsilicide phase shift patterns 17 a, 17 b and 17 c with a microscopicdefect developed on a quartz substrate 2 and a space portion 4 definedbetween the patterns 17 a, 17 b and 17 c.

(a) First, as shown in FIG. 11A, the microscopic defect of an oxidenitride film of molybdenum silicide is completely removed by FIBsputtering, leaving a thin gallium doped quartz layer 19 in the quartzsubstrate 2.

(b) Then, as shown in FIG. 11B, the gallium doped quartz layer 19 iseliminated by a gas assisted FIB etching process using a xenondifluoride (XeF₂) 20 and a FIB 7. As the gallium doped quartz layer 19is removed by the etching, a recess 21 is formed in the quartz substrate2 beneath the repaired region from which the gallium doped quartz layer19 is eliminated, as shown in FIG. 11C. The recess 21 can be so shallowas to give no interruption in an image of the pattern projected on awafer.

As shown in FIG. 12B, when the phase at the recess 21 to be repaired isshifted 360 degrees from the phase at the non-defect surface of thequartz substrate, no phase difference occurs in the pattern defectrepairing.

Although the laser etching or the gas assisted FIB etching with thexenon difluoride 20 is used for removing the gallium doped molybdenumsilicide layer 18 (See FIG. 10B(a)) or the gallium doped quartz layer 19(See FIG. 11A(a)), other appropriate processes may equally be appliedsuch as alkali wet etching using a solution of potassium hydroxide (KOH)or sodium hydroxide (NaOH) for eliminating gallium and dry etching byselective plasma etching of a gallium container layer.

THIRD EMBODIMENT

Third embodiment of the present invention pertains a method of maskrepairing a microscopic defect 6 a generated on a phase shift mask 22.The phase shift mask 22 of the third embodiment is composed ofchromium/molybdenum silicide patterns 23 a, 23 b and 23 c formed on atransparent quartz substrate 2. Each of the chromium/molybdenum silicidepatterns 23 a, 23 b and 23 c consists of the corresponding phase shiftpattern 17 a, 17 b or 17 c made of an oxide nitride of molybdenumsilicide and a chromium film 24 a, 24 b or 24 c provided on the phaseshift pattern 17 a, 17 b or 17 c, respectively. That is, the chromiumfilms 24 a, 24 b and 24 c are multi-layers, or composite films,comprising chromium layers and chromium oxide layers developed on thechromium layers, respectively.

In the boundary between shots, the lights penetrating the phase shiftfilms overlap, when the mask pattern is projected on the wafer, so thatthe resist film formed on the wafer is unintentionally exposed. It isnecessary to shield the perimeter of the mask to prevent this, namelythe part disposed at the boundary between shots on the wafer must becovered. Generally, the chromium film, which sufficiently shields thelight in this region, is employed for this purpose. This is called “thechromium frame.” Next the general manufacturing process of themolybdenum silicide phase shift mask with the chromium frame will beshown.

(a) First, a composite layer, comprising a molybdenum silicide phaseshifter film and a chromium film developed on the phase shifter film, isdeposited on the quartz substrate 2. Then, a resist film is coated onthe surface of the mask material. And the resist film is delineated to adesired pattern by exposing the resist film with an electron beamemitted from an electron beam lithography system. Using the pattern ofthe resist film as an etching mask, both the chromium film and themolybdenum silicide phase shifter film are etched, e.g. by reactive ionetching (RIE), to form patterns of the molybdenum silicide phase shifterfilms 17 a, 17 b and 17 c. Then, the resist film of the etching mask isremoved. In addition, another resist film is coated on the chromiumfilm, and the image of chromium frame is drawn on the resist film.Thereafter, the chromium etching is carried out again to remove thechromium films except for the chromium frame region, using the resistfilm mask to delineate the chromium frame. Then, the resist film isremoved, and the molybdenum silicide phase shift mask with the chromiumframe is completed. In the fourth embodiment of the present invention,the defect inspection is carried out, before the above process ofchromium frame delineation. That is, the repairing of the defect isexecuted before the chromium film on the molybdenum silicide film,except for the chromium frame region, is removed. Referring to FIG. 13A,the chromium films 24 a, 24 b and 24 c are not removed but remain on themolybdenum silicide phase shifter films 17 a, 17 b and 17 c,respectively. The mask pattern comprises line patterns of thechromium/molybdenum silicide patterns 23 a, 23 b and 23 c having thechromium films 24 a, 24 b and 24 c disposed on the phase shifter films17 a, 17 b and 17 c. A space pattern 4 is sandwiched between thechromium/molybdenum silicide patterns 23 a and 23 b. Further, anotherspace pattern 4 is sandwiched between the chromium Imolybdenum silicidepatterns 23 b and 23 c. It is now assumed that the microscopic defect 6a extends from the left edge of the line pattern 23 b.

(b) As shown in FIG. 13B, the chromium film 24 b of the microscopicdefect 6 a is etched by a gas assisted FIB etching process with theetching gas 8 being supplied. At FIB 7, gallium ions accelerated byvoltage of 20 kV, having a current of 50±10 pA and a beam diameter of0.2 μmφ, are employed. In the third embodiment of the present invention,since the chromium films 24 a, 24 b and 24 c are located on themolybdenum silicide phase shifter films 17 a, 17 b and 17 c, the patternfilms are hardly charged up at the step of imaging with the FIB 7. Thisimproves the S/N ratio between the chromium/molybdenum silicide patterns23 a, 23 b and 23 c and the space portions 4 and 4, thus enhancing thequality of a projected image and providing a stable accuracy of patterndefect repairing. Even if the microscopic defect 6 a has an undulatedsurface, the end point of etching process of the gas assisted FIBetching can be monitored to finish at the surface of the defect or maskrepaired region with a substantially flat configuration. Moreparticularly, the end point of the etching process is detected bycounting the number of chromium ions with a secondary ion detector whenthe surface of the repaired region becomes substantially flat. Indetail, as stated in the first embodiment, a thin chromium film 9 a isremaining where the microscopic defect 6 a was present as shown in FIG.13C (a). As explained in the first embodiment, the judgment over the endof the etching is more delayed at the perimeter of the microscopicdefect 6 a than in a central region of the microscopic defect 6 a. Thatis, the detected number of chromium ions is more quickly reduced in theperimeter opposite to the adjacent edge region of the microscopic defect6 a than in the central region. Hence, the opposite edge region willremain thicker, forming the uneven thin chromium film 9 a, after the gasassisted FIB etching of the microscopic defect 6 a, as shown in FIG.13C. More typically, the perimeter of the thin chromium film 9 a of themicroscopic defect 6 a ranges from 15 nm to 30 nm. The thickness of thecentral region of the microscopic defect 6 a after the gas assisted FIBetching is smaller than 30 nm, for example, substantially 0.3 nm to 5nm.

(c) Then, as shown in FIG. 13D, the remaining chromium film 9 a and themolybdenum silicide phase shifter film 17 b of the defect 6 a is etchedby repeating the same gas assisted FIB etching process. The etching ofthe molybdenum silicide film may be carried out by an FIB sputteringprocess, stopping the supply of the etching gas. However, when thesupply of the etching gas is changed, the irradiation area of the FIBmay be shifted, deteriorating the etching performance so that highaccuracy cannot be established. The positional shift of nozzles forsupplying the etching gases may change the electric field distributions,hence changing the location of the beam. Accordingly, the thirdembodiment of the present invention preferably employs the gas assistedFIB etching process with same etching gas for both the chromium films 24a, 24 b and 24 c and the phase shift films 17 a, 17 b and 17 c. The gasassisted FIB etching may form riverbeds around the perimeter of themicroscopic defect 6 a as explained previously. For compensation, theirradiation area of the ion beam directed towards the microscopic defect6 a on the transparent quartz substrate 2 is inwardly narrowed by 0.3 nmto 200 nm from the edge of the microscopic defect 6 a. Preferably, it isnarrowed by half of the beam diameter of the FIB. Considering the beamdiameter of the FIB, the area is inwardly narrowed, for example, by 100nm from the edge of the microscopic defect 6 a. Also, the microscopicdefect 6 a is etched to leave a thin layer of the molybdenum silicidethat is not higher than 30 nm in thickness so that the quartz substrateunder the microscopic defect 6 a is prevented from being completelyexposed to the FIB. As a result, a gallium doped molybdenum silicidelayer 18 remains where the microscopic defect 6 a was present as shownin FIG. 13E.

(d) Then the gallium doped molybdenum silicide layer 18 derived from themicroscopic defect 6 a is removed by exposure to a laser beam. Themolybdenum silicide layer 18 of the microscopic defect 6 a containsgallium ions implanted by the FIB and enables absorption of more energyfrom the laser beam thus being eliminated at a higher efficiency.Accordingly, even when the irradiation area 10 of the laser beam isdetermined not to overlap the molybdenum silicide phase shifter film 17b as shown in FIG. 13E, the gallium doped molybdenum silicide layer 18adjacent to the edge of the molybdenum silicide phase shifter film 17 bcan be eliminated without difficulty. Consequently, as shown in FIG.13F, the mask pattern can be repaired to a desired definite shape, afterthe gallium doped molybdenum silicide layer 18 of the microscopic defect6 a having been eliminated completely. Similar to the second embodiment,this step may be carried out by completely removing the molybdenumsilicide of the microscopic defect 6 a so as to form the gallium dopedquartz layer in the quartz substrate 2, and eliminating the galliumdoped quartz layer with a xenon difluoride gas assisted FIB etchingprocess (See FIG. 11B). As the mask repaired by the method of the thirdembodiment of the present invention has the chromium film 24 b disposedon the molybdenum silicide phase shifter film 17 b, the molybdenumsilicide phase shifter film 17 b, which is easily etched by the xenondifluoride gas 20, can be protected by the chromium film 24 b. Also, theremoval of the gallium doped molybdenum silicide layer or the galliumdoped quartz layer may be conducted successfully by any otherappropriate process such as alkali wet etching using a solution ofpotassium hydroxide (KOH) or sodium hydroxide (NaOH) for dissolvinggallium. Further, the gallium doped molybdenum silicide layer or thegallium doped quartz layer may be removed by dry etching, such as byselective plasma etching, as well as by the laser etching and the xenondifluoride gas assisted FIB etching.

(e) Finally, as shown in FIG. 13G, the chromium films 24 a, 24 b and 24c on the molybdenum silicide phase shifter film 17 a, 17 b and 17 c arepeeled off and then, the method for repairing pattern defect accordingto the third embodiment of the present invention is ended. As shown inFIG. 13G, the phase shifter film 17 b has an oblique sidewall at leftedge, differing from that of the remaining vertical sidewall of thephase shifter films 17 a and 17 c. The oblique sidewall corresponds tothe repaired portion, and can easily be recognized, since the obliquesidewall is brighter than other vertical edges in reflective images.Although it may depend on the etching condition of after the gasassisted FIB etching, the oblique angle of the sidewall at the repairedportion may be less than 10 degrees from the normal direction of themask substrate. The phase shifter film 17 b has the vertical sidewall atthe right edge, obviously. By the existence of the bright obliquesidewall at the repaired portion, the left edge of the phase shifterfilm 17 b may show a small bite in a plan view, but the bite is so smallthat the left edge of the phase shifter film 17 b can be regarded as astraight line in a practical sense of photolithography. As set forthabove, the pattern defect repairing method of the third embodiment ofthe present invention allows any defect on a phase shift mask having achromium film provided on a phase shifter film of a molybdenum silicideto be successfully eliminated while maintaining the edge at higherprecision, minimizing damage to the etched region, or suppressing therecess formation on the surface of the quartz substrate, and making thesurface of a repaired region flat.

FOURTH EMBODIMENT

The present invention is applicable to the isolated defect 6 c disposedmidway between lines 3 a and 3 b as shown in FIG. 1C. When themicroscopic defect 6 c is sputtered by a FIB with an assistant gas forchromium film etching so that the etching is finished when the number ofchromium ions is decreased 70 to 80% in the end point detection level, athin chromium film 9 b remains where the microscopic defect 6 c waspresent, as shown in FIG. 14. The perimeter of the thin chromium film 9b ranges I nm to 30 nm in thickness. The thickness of the central regionof the thin chromium film 9 b is smaller than 30 nm, for example,substantially 0.3 nm to 5 nm. Then, substantially same as the firstembodiment, the thin chromium film 9 b is eliminated by the laserirradiation.

As shown in FIG. 15A, in a fourth embodiment of the present invention,eight chromium light-shielding squares 311, 312, 313, 321, 323, 331,332, and 333 delineated on a transparent quartz substrate 2 are shown.Each of the chromium light-shielding lines squares 311, 312, 313, 321,323, 331, 332, and 333 is composed of a layered structure consisting ofa chromium layer and a chromium oxide layer provided on the chromiumlayer. The center of the chromium light-shielding lines squares 311,312, 313, 321, 323, 331, 332, and 333, the isolated. The mask defectrepairing method according to the fourth embodiment of the presentinvention will now be described.

(a) First, as substantially similar to the fist embodiment, the isolateddefect 6 is sputtered by a gas assisted FIB etching process for chromiumfilm etching. The assistant gas is sprayed over the mask surface. Theexposure area about the isolated defect 6 to the ion beam, is inwardlynarrowed by 0.3 nm to 200 nm from the edge of the isolated defect 6,preferably, it is narrowed by a half of the FIB diameter. The end pointof the etching is determined by counting the number of chromium ions illthe etched region with a secondary ion detector. The etching proceeds tothe point where the surface of the quartz substrate is nearly exposed,and stops, before the quartz substrate beneath the isolated defect 6 iscompletely exposed to the FIB.

(b) As a result, a non-uniform thin chromium film 9 b remains where theisolated defect 6 was present. More typically, the thin chromium film 9b of the isolated defect 6 ranges from 15 nm to 30 nm at the perimeter.The thickness of the central region of the thin chromium film is smallerthan 30 nm, for example, substantially 0.3 nm to 5 nm. FIG. 16 shows animage intensity profile taken along line XV—XV of FIG. 15B. There is 12%reduction of transmissivity at the perimeter of the isolated defect 6,and there is transmissivity reduction of about 8% on central portion ofthe isolated defect 6. In FIG. 16, “R” represents the repaired portion.

(c) Next, the thin chromium film 9 b is etched away by an acid solution.The repaired portion image intensity distribution after the thinchromium film 9 b was removed is shown in FIG. 17. In FIG. 17, “R”represents the repaired portion. Both at perimeter and at centralportion, a transmissivity over 96% is shown. That is, FIG. 16 shows therecovery of the transmissivity reduction by the wet etching. Here, anyacid solution generally employed in the mask fabrication process can beapplied to remove the thin chromium film 9 b. In the case of thisembodiment, for example, the 3:1 solution of sulfuric acid (H₂SO₄) andhydrogen peroxide (H₂O₂) heated to 105° C. can be used.

As mentioned above, it is possible to repair the isolated defect, whichoccurred on the chromium mask, by the repairing method of pattern defectaccording to the fourth embodiment, without generating damage to themask substrate. In this fourth embodiment, the repairing of mask inwhich normal square patterns and the isolated defect are disposed isdescribed. However, it is possible to repair the protruding defect fromthe normal pattern, or the macroscopic defect contacting the edge ofnormal pattern, in which the effectiveness shown by the first and fourthembodiments are simultaneously achieved.

MANUFACTURING SEMICONDUCTOR DEVICE

The mask repaired by the present invention can be employed formanufacturing semiconductor devices such as LSI, VLSI, ULSI, GSIincluding nMOS FETs, pMOS FETs, CMOS FETs, BJTs or SITs. FIG. 18 shows asimplified flowchart for manufacturing semiconductor devices.

(a) In step S101, the set of layout data for the semiconductor devicessuch as LSI, VLSI, ULSI, or GSI is designed by computer aided design(CAD) method. On the other hand, in step S102, mask blanks are prepared.For example, on a transparent quartz substrate, an oxide nitride ofmolybdenum silicide film and a chromium film deposited by CVD method,vacuum evaporation method, or sputtering method. And further, a resistfilm is coated on a chromium film.

(b) In step S111, using an optical, electron beam, ion beam, or X-raylithography system, the required set of mask patterns are delineated onthe mask blanks prepared by step S102. In this pattern generation step,the set of layout data prepared by the step S101 is employed. And usingthe delineated resist patterns as etching masks, chromium films andoxides nitride of molybdenum silicide films are cut by RIE, or ionetching, etc. Then the resist films are removed, and the set of photomasks are fabricated.

(c) The fabricated mask patterns are inspected in step S112. And, if thedefect is found in any of the set of photo masks, the correspondingdefect is repaired in step S113, according to the procedure such asstated in first to fourth embodiments.

(d) After completion of the pattern defect repairing step, thesemiconductor device manufacturing process in step S114 is conductedwith the set of photo masks, which includes the repaired mask accordingto one of the first to fourth embodiment.

Details of the semiconductor device manufacturing process in step S114is shown in FIG. 19.

(a) In step S201, objective materials, such as a semiconductor wafer,insulating film, and conductive film are prepared. The semiconductorwafer may include a silicon wafer, gallium arsenide (GaAs) water, orsemiconductor wafers comprising other compounds. The step S201 mayinclude a planarization step of the surface of the wafers by chemicalmechanical polishing (CMP), an epitaxial growth step, CVD step, vacuumevaporation step, sputtering step, etc.

(b) Then on the objective materials, a resist film is coated in stepS202. In step S202, the following photolithography process is conducted.That is the resist film is pre-baked and exposed by optical lay throughthe mask repaired by the method according to the present invention. Andthe resist film is developed, rinsed, post-baked and cured.

(c) And using the resist film delineated by the step S202 as the etchingmask, the objective materials are selectively etched in step S203. Theselective etching may be conducted by known dry etching or wet etching.On the other hand, using the resist film delineated by step S202 as thediffusion mask (implantation mask), the objective materials may beselectively ion implanted in step 204.

(d) Then the resist film employed in the step S203, or in the step S204is removed in step S205. After that, in step S206, the semiconductorwafer is annealed. The annealing may include the drive-in process.Further, using the oxide film etched in the step S203 as a diffusionmask, a thermal diffusion process employing the predeposition can alsobe conducted in step S206. Then, the process flow can return to theabove-mentioned step S201 for further depositing thin film on thesemiconductor wafer. Then the step S202 is also conducted to proceed tostep S203, S204, . . . , and this loop continues until the requiredstructure is completed. If pluralities of loops are repeated accordingto the prescription of the process design, it is enough that at leastone of the steps 202 repeated contains the photolithography processusing the repaired mask mentioned in the first to fourth embodiments.

FIG. 20 outlines relatively simple manufacturing processes according tothe flow chart shown in FIG. 19. That is, FIG. 20 outlines a simpleexample of the manufacturing processes of an nMOS FET, which areexplained as follows:

(a) First, into an n-type silicon substrate in which phosphorus (P) isalready doped, a Si₃N₄ film is deposited by a CVD method. And on theSi₃N₄ film, resist film is coated. By a first photolithography processemploying a mask, which may be the repaired mask by the presentinvention, a resist film is delineated. And using the resist film asmask, the Si₃N₄ film is patterned so that only device regions of theSi₃N₄ film are selectively left, and the resist film is removed. Usingthe Si₃N₄ film as an anti-oxidation film, oxidation (LOCOS) is carriedout to form device-isolation insulator films with a thickness of 600 nm.Prior to device-isolation oxidation, channel-stop ions of p-typeimpurity boron (¹¹B⁺) are implanted at 100 KeV, with dosage of1×10¹³/cm² into regions where the Si₃N₄ film was removed, thuspreventing inversion of the surface of silicon substrate. In thedevice-insulation regions where the Si₃N₄ film was removed, a thickoxide film of 600 nm is formed, under which a p-type impurity boron(¹¹B⁺) is introduced to prevent surface inversion. Then, the Si₃N₄ filmused in LOCOS is removed.

(b) On the Si₃N₄ film, another resist film is coated. By a secondphotolithography process employing another mask (second mask), which maybe the repaired mask by the present invention, the resist film isdelineated. And using the resist film as mask, into regions which act asactive regions (or transistor regions), ions of boron (¹¹B⁺) areimplanted at 100 KeV, with dosage of 1×10¹³/cm² to form a p-type well,and the resist film is removed. For the ion implantation of boron, thesecond mask (second photolithography process) can be omitted, accordingto the device design. And then the drive-in diffusion is conducted toprovide desired depth and concentration.

(c) A thin oxide film of 10 nm thickness, which acts as a dummy oxidefilm, is formed in the surfaces of the p-type well. And on the dummyoxide film, another resist film is coated. By a third photolithographyprocess employing still another mask (third mask), which may be therepaired mask by the present invention, a resist film is delineated. Andusing the resist film as mask, through the dummy oxide film areimplanted ions of boron (¹¹B⁺) at 100 KeV, with dosage of 7×10¹²/cm² tocontrol the threshold voltage (Vth). And the resist film is removed. Forthe Vth control ion implantation, the third mask (third photolithographyprocess) can be omitted, according to the device design.

(d) And on the dummy oxide film, still another resist film is coated. Bya fourth photolithography process employing still another mask (fourthmask), which may be the repaired mask by the present invention, a resistfilm is delineated. And using the resist film as mask, ions of boron(¹¹B⁺) to prevent punch-through are implanted at a higher accelerationenergy of 80 KeV, with dosage of 5×10¹²/cm² so that high-concentrationp-type regions are placed beneath the channel regions. And the resistfilm is removed. For the punch-through prevention ion implantation, thefourth mask (fourth photolithography process) can be omitted, accordingto the device design. Further the punch-through prevention ionimplantation, by itself, can be omitted, according to the device design.

(e) The dummy oxide film is removed to form a gate oxide film of 10 nmthickness. On that gate oxide film, a polysilicon film, which acts asgate electrodes, is deposited. And on the polysilicon film, stillanother resist film is coated. By a fifth photolithography processemploying still another mask (fifth mask), which may be the repairedmask by the present invention a resist film is delineated. And using theresist film as mask, the polysilicon film is cut by RIE to form the gateelectrodes. And the resist film is removed. Further, the patternedpolysilicon surfaces are post-oxidized. And on the polysilicon film,still another resist film is coated. By a sixth photolithography processemploying still another mask (sixth mask), which may be the repairedmask by the present invention, a resist film is delineated. And usingthe resist film as a mask, and also using thus patterned and oxidizedpolysilicon as a mask, ions of n-type impurity arsenic (⁷⁵As⁺) areimplanted at 30 KeV, with dosage of 5×10¹⁵/cm² into silicon regionswhich act as source or drain regions. At the same time, the arsenic(⁷⁵As⁺) ions are implanted into the polysilicon region, which acts asgate electrodes. And the resist film is removed. For the arsenic ionimplantation, the sixth mask (sixth photolithography process) can beomitted, according to the device design, since the arsenic ionimplantation is the well-known self-alignment process by nature. Afterthat, the surfaces are covered with a CVD oxide (SiO₂) film and undergoheat treatment to activate the arsenic (⁷⁵As⁺).

(f) And on the CVD oxide film, still another resist film is coated. By aseventh photolithography process employing still another mask (seventhmask), which may be the repaired mask by the present invention, a resistfilm is delineated. And using the resist film as a mask contact holesare opened in the CVD oxide film. And the resist film is removed.Further, on the CVD oxide film and into those created openings, Al orother metal is deposited by vacuum evaporation or sputtering. Then, onthe CVD oxide film, still another resist film is coated. By an eighthphotolithography process employing still another (eighth mask), whichmay be the repaired mask by the present invention, a resist film isdelineated. And using the resist film as mask, this metal is patternedby RIE etc., to form a metal wiring pattern. And the resist film isremoved to finish the manufacturing process of nMOS FETs.

In the above manufacturing processes of an nMOS FET, it is enough thatat least one of the first to eighth masks is the repaired mask mentionedin the first to fourth embodiments.

Various modifications will become possible for those skilled in the artafter receiving the teachings of the present disclosure withoutdeparting from the scope thereof.

What is claimed is:
 1. A method for repairing a pattern defectcomprising: (a) determining the irradiation area for an ion beamdirected towards a defect pattern film material formed on a masksubstrate, the defect pattern film material being an opaque materialdifferent from a transparent material of the mask substrate, bynarrowing the irradiation area by a predetermined distance inwardly fromthe edge of the defect pattern film material; (b) focusing the ion beamonto its irradiation area to remove a part of the defect pattern filmmaterial from its surface so as to leave a thin layer of the defectpattern film material on the mask substrate, configured such that theion beam does not attack a surface of the mask substrate; and (c)removing only the thin layer by using a laser beam so as not to ablate anormal pattern film material neighboring the defect pattern filmmaterial, the normal pattern film material being made of the opaquematerial.
 2. The method of claim 1, wherein the predetermined distancefrom the edge of the defect pattern film material is 0.3 nm to 200 nm.3. The method of claim 1, wherein the predetermined distance from theedge of the defect pattern film material is half of the diameter of thefocused ion beam.
 4. The method of claim 1, wherein, in the step offocusing the ion beam, a pattern film material formed on the masksubstrate at an interface between the defect pattern film material and anormal pattern film material neighboring to the defect pattern filmmaterial is completely removed.
 5. The method of claim 1, wherein thethin layer has an uneven thickness profile, and its maximum thickness is1 nm to 30 nm.
 6. The method of claim 1, wherein, in the step ofremoving the thin layer, the irradiation area of the laser beam is sodetermined as not to overlap the edge of a normal pattern film material.7. The method of claim 1, wherein the mask substrate is quartz.
 8. Themethod of claim 7, wherein a main component of the defect pattern filmmaterial is chromium.
 9. The method of claim 8, wherein the defectpattern film material contains a chromium oxide.
 10. The method of claim8, wherein the step of leaving the thin layer is carried out by a gasassisted focused ion beam etching, employing a gas having a etchingselectively between the defect pattern film material and the masksubstrate.
 11. The method of claim 7, wherein a main component of thedefect pattern film material is molybdenum silicide.
 12. The method ofclaim 7, wherein a main component of the defect pattern film material isa molybdenum silicide compound.
 13. The method of claim 7, wherein thedefect pattern film material formed on the mask substrate comprises afirst pattern film containing molybdenum suicide and a second patternfilm containing chromium, the second pattern film is disposed on thefirst pattern film.
 14. The method of claim 13, wherein the step ofleaving the thin layer includes etching the second pattern film by a gasassisted focused ion beam etching, employing a gas having a etchingselectively between the second pattern film material and the masksubstrate.
 15. The method of claim 11, wherein the focused ion beamcontains gallium ions and the thin layer contains a gallium dopedmolybdenum silicide.
 16. The method of claim 14, wherein the firstpattern film is etched by the gas assisted focused ion beam etching. 17.The method of claim 16, wherein the focused ion beam contains galliumions and the thin layer contains a gallium doped molybdenum silicide.18. A photo mask repaired by a method comprising focused ion beametching so as to leave a thin layer of the defect pattern film materialon the mask substrate and removing the thin layer by using a laser beam,the photo mask comprising: (a) a mask substrate having substantiallyflat surface; and (b) a pattern delineated on the mask substrate, thepattern has an edge, the edge has a localized specific side wall havingan inclination angle differing from that of remaining sidewall, thelocalized specific side wall representing a repaired portion by thefocused ion beam etching and the laser beam removing.
 19. The photo maskof claim 18, wherein decrease in the image intensity through said masksubstrate neighboring to said specific side wall is not higher than 5%compared with that of other portion.
 20. A method for manufacturing asemiconductor device comprising: (a) generating patterns with a patternfilm material on a mask substrate so as to fabricate a photo mask, thepattern film material is an opaque material different from a transparentmaterial of the mask substrate; (b) inspecting a defect pattern filmmaterial made of the pattern film material on the mask substrate; (c)repairing the defect pattern film material comprising: determining theirradiation area for an ion beam directed towards the defect patternfilm material, by narrowing the irradiation area by a predetermineddistance inwardly from the edge of the defect pattern film material;focusing the ion beam onto its irradiation area to remove a part of thedefect pattern film material from its surface so as to leave a thinlayer of the defect pattern film material on the mask substrate,configured such that the ion beam does not attack a surface of the masksubstrate; and removing only the thin layer by using a laser beam so asnot ablate a normal pattern film material neighboring the defect patternfilm material, the normal pattern film material being made of the opaquematerial; and (d) fabricating a semiconductor device employing saidrepaired photo mask.